Miniature tactical HF antenna

Abstract

An improved miniature antenna is disclosed which provides an electrically short radiation pattern by providing shielding of selected portions of a current carrying conductor forming a loop antenna. The shielding is provided so that the shielded portion of the loop antenna does not cancel the radiation from an unshielded radiating portion of the antenna, thereby producing a uniform radiation pattern. A plurality of the current carrying elements formed by the shielded and unshielded portions may be coupled in a series and parallel relationship to provide optimum impedance matching at the frequency of operation of a transmitter or receiver.

What is claimed is: 
     
       1. An antenna element comprising: A first electrical conductor;   an electrically conductive tube having a first tube end and a second tube end;   a second electrical conductor having a first end extending along and within said tube from said first tube end to said second tube end, said first end of said second electrical conductor coupled to said first electrical conductor and said second end of said second electrical conductor coupled to said second tube end; and   a third electrical conductor having a first end coupled to the first tube end and extending along and within said tube and spaced substantially parallel to said second electrical conductor and having a second end extending from said second tube end.   
     
     
       2. The element of claim 1 wherein said tube is cylindrical and has inner and outer walls and said second and third electrical conductors are spaced parallel to said inner wall. 
     
     
       3. A miniature antenna system comprising: a plurality of antenna elements forming multiple closed loop transmission lines;   means for shielding a first portion of each of said plurality of antenna elements such that a second unshielded portion of each antenna element forms an antenna radiating and receiving portion for transmitting and receiving radio frequency radiation; and   a plurality of relays coupled to selectively parallel and serially couple multiple ones of said closed loop transmission lines to alter the effective electrical length of the antenna formed by said closed loop transmission lines.   
     
     
       4. The system of claim 3 wherein said means for impedance matching further includes means for translating the impedance of said plurality of radiating and receiving portions to 50+jO ohms. 
     
     
       5. The system of claim 3 wherein each of said selected closed loop transmission lines are coupled to have a common coupling point for minimizing circulating currents. 
     
     
       6. The system of claim 3 wherein said antenna elements are configured to form an omnidirectional antenna. 
     
     
       7. An antenna system comprising: a plurality of antenna elements forming multiple closed loop transmission lines, each of said antenna elements having a first unshielded section which includes a first electrical conductor having first and second ends, and a second shielded section wherein said unshielded section forms an antenna radiating and receiving portion for transmitting and receiving radio frequency radiation;   said second shielding section including;   an electrically conductive tubular member having first and second ends;   a second electrical conductor disposed within and extending through said tubular member and spaced therefrom and having a first end electrically coupled to the first end of said first conductor and a second end coupled to the second end of said tubular member;   a third electrical conductor disposed within and extending through said tubular member and spaced therefrom and having a first end coupled to the first end of said tubular member and a second end projecting from the second end of said tubular member; and   means for coupling said plurality of closed loop transmission lines for impedance matching said antenna for selected frequency band of operation.   
     
     
       8. The antenna of claim 7 further comprising an electrically conductive base, said second ends of said first conductor and said third conductor extending through and electrically insulated from said base.